Trouble getting the free storage pane

so i get all the way to the point where it says "link your GW account." then it prompts me for an account and password. what do i type in there? i'm already logged in on the NCSoft store, so i tried my game log in that i use to get to character selection. no go. i tried my XTH log in. no go. what exactly am i supposed to type in? i contacted support, and they've been sending me cookie cutter responses without answering my simple "what do i type in" question.

thanks for the help.

your PlayNC account.
there has been problems since it started.